The present invention relates generally to electro-deposition (electroplating) systems for applying a coating to an assembly, and more particularly to an electro-deposition system that employs a drag through electrolyte bath.
It is common practice to coat vehicle bodies with an anti-corrosion coating by employing an electro-deposition process. A type of system employed for high volume vehicle production is a drag through type of electro-deposition assembly. Conventional drag through electro-deposition assemblies include an electrolyte bath through which the vehicle bodies are dragged as they are undergoing the electro-deposition process. In these conventional assemblies, typically only two or three large rectifiers are employed, with each supplying very high current to a relatively large number of anodes located in the tank. As such, they are generally custom built rectifier/anode assemblies that have relatively limited process controllability and only voltage control. Accordingly, the costs for such systems, as well as the cost of rectifier backup for these systems is more expensive than is desired. Moreover, they do not lend themselves to adjusting the system to accommodate increases in vehicle production.
Another type of electro-deposition system for vehicle bodies employs an index tank. In an index tank the vehicle body is dropped straight down into the tank, the electro-deposition takes place, and then the vehicle is lifted straight up out of the tank. One type of index tank system uses multiple pairs of anodes, with each pair of anodes powered by a direct current source. While the particular vehicle body is stationary in the index tank, a constant current is applied to each pair of anodes to cause the desired amount of corrosion protection to be applied to the various parts of the vehicle body. While eliminating the small number of high power rectifiers that are employed with drag through tanks, index tanks are not practical for high volume production of vehicles—the through-put capability of each index tank is generally too low.